1 files changed, 68 insertions, 0 deletions
diff --git a/lib/i-ring.c b/lib/i-ring.c
new file mode 100644
index 0000000..659c61c
--- /dev/null
+++ b/lib/i-ring.c
@@ -0,0 +1,68 @@
+/* a simple ring buffer
+   Copyright (C) 2006, 2009-2022 Free Software Foundation, Inc.
+
+   This file is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation, either version 3 of the
+   License, or (at your option) any later version.
+
+   This file is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* written by Jim Meyering */
+
+#include <config.h>
+#include "i-ring.h"
+
+#include <stdlib.h>
+
+void
+i_ring_init (I_ring *ir, int default_val)
+{
+  int i;
+  ir->ir_empty = true;
+  ir->ir_front = 0;
+  ir->ir_back = 0;
+  for (i = 0; i < I_RING_SIZE; i++)
+    ir->ir_data[i] = default_val;
+  ir->ir_default_val = default_val;
+}
+
+bool
+i_ring_empty (I_ring const *ir)
+{
+  return ir->ir_empty;
+}
+
+int
+i_ring_push (I_ring *ir, int val)
+{
+  unsigned int dest_idx = (ir->ir_front + !ir->ir_empty) % I_RING_SIZE;
+  int old_val = ir->ir_data[dest_idx];
+  ir->ir_data[dest_idx] = val;
+  ir->ir_front = dest_idx;
+  if (dest_idx == ir->ir_back)
+    ir->ir_back = (ir->ir_back + !ir->ir_empty) % I_RING_SIZE;
+  ir->ir_empty = false;
+  return old_val;
+}
+
+int
+i_ring_pop (I_ring *ir)
+{
+  int top_val;
+  if (i_ring_empty (ir))
+    abort ();
+  top_val = ir->ir_data[ir->ir_front];
+  ir->ir_data[ir->ir_front] = ir->ir_default_val;
+  if (ir->ir_front == ir->ir_back)
+    ir->ir_empty = true;
+  else
+    ir->ir_front = ((ir->ir_front + I_RING_SIZE - 1) % I_RING_SIZE);
+  return top_val;
+}